COAHUILA STATE, Mexico — The federal government says 26,000 people have been reported missing across Mexico since 2006, and yet just two states have a local prosecutor’s office dedicated to the investigation of such cases.

Even there, those who have disappeared are rarely found. Some have been caught up in the drug trade; others forcibly recruited to work for the gangs. Cases of mistaken identity are also common, and some are just in the wrong place at the wrong time. Across the country, very few cases are properly investigated, and reports of the involvement of authorities are frequent.